The present invention relates to a push button device equipped with a plurality of push buttons, and more specifically, to a mechanism for preventing simultaneous locking of more than one pusn button in a device having a plurality of push buttons.
Electric circuits often operate erroneously when two or more push buttons of a push button device having a plurality of push buttons are inadvertently actuated at one time, particularly when the push buttons are of the type locked in their actuated condition. Consequently, such a locked-type push button device should be so constructed that all of the buttons actuated return to their initial state and do not lock whenever two or more push buttons are simultaneously actuated.
Lock-type push button devices have been proposed for use as the channel selector employed as a tuner for modern television sets since conventional channel selectors typically involved clumsy operation for selecting the channels, particularly when the channels are to be selected in the UHF band.
FIG. 1 is a diagram illustrating the appearance of a channel tuner employing push buttons for selecting various channels. After a switch 1 for selecting the appropriate band has been set to a desired band, one of the push buttons 2 for selecting the channels is actuated to select a desired channel easily. With channel tuners of this type, however, the many number of channels in the VHF, UHF, and perhaps, CATV bands require increased number of push buttons arrayed with only a small distance between them. Therefore, unless they are actuated carefully, neighboring push buttons will often be depressed simultaneously and become locked, and the desired channel would thus not often be selected properly.
With the locked-type push button device for use in channel tuners, therefore, the push buttons should not be locked but should return to the non-depressed position when two or more push buttons are simultaneously depressed to prevent erroneous operation or erroneous selection of a channel.
Conventional channel tuners employing push buttons have not typically been provided with structures preventing simultaneous locking of two push buttons. Devices for preventing the simultaneous locking of two adjacent switches used in other fields are complex in construction and their increased manufacturing costs make them prohibitive for use in channel tuners.